feat: add cpp solution to lc problem No.0008 (#4442)

Author: gaganxsaini

solution/0000-0099/0008.String to Integer (atoi)/README.md

@@ -214,6 +214,36 @@ class Solution {
 }
 ```
 
+#### C++
+
+```cpp
+class Solution {
+public:
+    int myAtoi(string s) {
+        int i = 0, n = s.size();
+        while (i < n && s[i] == ' ')
+            ++i;
+
+        int sign = 1;
+        if (i < n && (s[i] == '-' || s[i] == '+')) {
+            sign = s[i] == '-' ? -1 : 1;
+            ++i;
+        }
+
+        int res = 0;
+        while (i < n && isdigit(s[i])) {
+            int digit = s[i] - '0';
+            if (res > INT_MAX / 10 || (res == INT_MAX / 10 && digit > INT_MAX % 10)) {
+                return sign == 1 ? INT_MAX : INT_MIN;
+            }
+            res = res * 10 + digit;
+            ++i;
+        }
+        return res * sign;
+    }
+};
+```
+
 #### Go
 
 ```go

solution/0000-0099/0008.String to Integer (atoi)/README_EN.md

@@ -160,19 +160,16 @@ class Solution:
         i = 0
         while s[i] == ' ':
             i += 1
-            # 仅包含空格
             if i == n:
                 return 0
         sign = -1 if s[i] == '-' else 1
         if s[i] in ['-', '+']:
             i += 1
         res, flag = 0, (2**31 - 1) // 10
         while i < n:
-            # 非数字，跳出循环体
             if not s[i].isdigit():
                 break
             c = int(s[i])
-            # 溢出判断
             if res > flag or (res == flag and c > 7):
                 return 2**31 - 1 if sign > 0 else -(2**31)
             res = res * 10 + c
@@ -190,17 +187,14 @@ class Solution {
         if (n == 0) return 0;
         int i = 0;
         while (s.charAt(i) == ' ') {
-            // 仅包含空格
             if (++i == n) return 0;
         }
         int sign = 1;
         if (s.charAt(i) == '-') sign = -1;
         if (s.charAt(i) == '-' || s.charAt(i) == '+') ++i;
         int res = 0, flag = Integer.MAX_VALUE / 10;
         for (; i < n; ++i) {
-            // 非数字，跳出循环体
             if (s.charAt(i) < '0' || s.charAt(i) > '9') break;
-            // 溢出判断
             if (res > flag || (res == flag && s.charAt(i) > '7'))
                 return sign > 0 ? Integer.MAX_VALUE : Integer.MIN_VALUE;
             res = res * 10 + (s.charAt(i) - '0');
@@ -210,6 +204,36 @@ class Solution {
 }
 ```
 
+#### C++
+
+```cpp
+class Solution {
+public:
+    int myAtoi(string s) {
+        int i = 0, n = s.size();
+        while (i < n && s[i] == ' ')
+            ++i;
+
+        int sign = 1;
+        if (i < n && (s[i] == '-' || s[i] == '+')) {
+            sign = s[i] == '-' ? -1 : 1;
+            ++i;
+        }
+
+        int res = 0;
+        while (i < n && isdigit(s[i])) {
+            int digit = s[i] - '0';
+            if (res > INT_MAX / 10 || (res == INT_MAX / 10 && digit > INT_MAX % 10)) {
+                return sign == 1 ? INT_MAX : INT_MIN;
+            }
+            res = res * 10 + digit;
+            ++i;
+        }
+        return res * sign;
+    }
+};
+```
+
 #### Go
 
 ```go
@@ -282,8 +306,6 @@ const myAtoi = function (str) {
 #### C#
 
 ```cs
-// https://leetcode.com/problems/string-to-integer-atoi/
-
 public partial class Solution
 {
     public int MyAtoi(string str)

solution/0000-0099/0008.String to Integer (atoi)/Solution.cpp

@@ -0,0 +1,25 @@
+class Solution {
+public:
+    int myAtoi(string s) {
+        int i = 0, n = s.size();
+        while (i < n && s[i] == ' ')
+            ++i;
+
+        int sign = 1;
+        if (i < n && (s[i] == '-' || s[i] == '+')) {
+            sign = s[i] == '-' ? -1 : 1;
+            ++i;
+        }
+
+        int res = 0;
+        while (i < n && isdigit(s[i])) {
+            int digit = s[i] - '0';
+            if (res > INT_MAX / 10 || (res == INT_MAX / 10 && digit > INT_MAX % 10)) {
+                return sign == 1 ? INT_MAX : INT_MIN;
+            }
+            res = res * 10 + digit;
+            ++i;
+        }
+        return res * sign;
+    }
+};